/*
import java.util.Scanner;

*/
/**
 * Created with IntelliJ IDEA.
 * Description:
 * User: HP
 * Date: 2022-04-29
 * Time: 14:03
 *//*

public class Sum {
    static int sum0(int n){
        assert (n>0)?true:false;
        if(n == 1){
            return 1;
        }else {
            return n+sum0(n-1);
        }
    }

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        while(sc.hasNext()){
            int n = sc.nextInt();
            System.out.println(sum0(n));
        }
    }
}
*/
